The present invention relates generally to plant molecular biology and genetic engineering employing recombinant DNA techniques. More particularly, the invention pertains to isolated DNA including an osmotin gene promoter, and recombinant DNA including a foreign gene under control of the osmotin gene promoter, and transformants including the recombinant DNA.
Osmotin and osmotin-like proteins (hereinafter "osmotins") and coding sequences for osmotin proteins have been studied extensively. Osmotins are a group of cationic proteins existing in at least two forms, one with a pl&gt;7.8 and another with a pl&gt;8.2.
Osmotins have been classified as members of the PR-5-type proteins of tobacco. Studies have shown that the synthesis and accumulation of osmotin mRNA are developmentally regulated and controlled by at least six hormonal or environmental signals, including abscisic acid (ABA), ethylene, tobacco mosaic virus invention, salinity, desiccation, and wounding in both cultured cells and whole plants of tobacco. For additional background information with respect to osmotins, reference can be made to the following publications: Singh et al., Plant Physiol., 85, 529-536 (1987); Singh et al., Plant Physiol., 90, 1096-1101 (1989); Singh et al., In NATO ASI Series, G19, pp. 67-87 "Environmental Stress in Plants", J. H. Cherry, ed (1989); LaRosa et al., Plant Physiol., 91, 855-861 (1989); Meeks-Wagner et al., Plant Cell, 1, 25-35 (1989); Grosset et al., Plant Physiol., 92, 520-527 (1990); Neale et al., Plant Cell, 2, 673-684 (1990); Roberts et al., J. Gen. Microbiol., 136, 1771-1778 (1990); Stintzi et al., Physiol. Mol. Plant Pathol., 38, 137-146 (1991); Woloshuk et al., Plant Cell, 3, 619-628 (1991); Singh et al., Plant Physiol. 79, 126-137 (1985); Richardson et al., Nature, 327, 432-434 (1987); Bol, In Temporal and Spatial Regulation of Plant Genes, D. P. S. Verma and R. B. Goldberg eds (New York: Springer-Verlag) pp. 201-221 (1988); Brederode et al., Mol. Biol., 17, 1117-1125 (1991); Linthorst, Crit. Rev. Plant Sci., 10, 123-150 (1991); LaRosa et al., Plant Physiol., 79, 138-142 (1985); La Rosa et al., Plant Physiol., 85, 174-185 (1987); Singh et al., Proc. Natl. Acad. Sci. USA, 84, 739-743.
Despite considerable study of the coding sequences for osmotins, the prior art has not provided identification of or characterized promoters for osmotin genes or explored potential uses of such promoters. This is despite the continuing need for additional promoters which are useful in genetic engineering techniques and which may provide highly advantageous temporal and/or spatial expression of genes. Such regulation of expression allows for great variability in the manner in which the promoter is used including the capacity to express gene products in response to particular applied environmental signals, or to express gene products in specific tissues or developmental stages in which the expression is maximally beneficial.
It has been discovered that regulation of osmotin protein expression in plants is controlled by the osmotin promoter. Fusion of the osmotin promoter to a heterologous gene results in unique temporal and spatial expression of the heterologous gene in transformed plants. The osmotin promoter is therefore a transcription regulatory element which can be used to control the expression of operably linked genes under unique conditions and in targeted tissues and developmental stages of transformed plants.